1. Field of the Invention
The present invention relates to a carrier indication method for a wireless communication system and related communication device, and more particularly, to a carrier indication method and communication device for indicating carriers of a carrier aggregation function in an LTE-Advanced system.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs). The LTE radio protocol stack includes the Layer 3, also known as the Radio Resource Control (RRC) layer, the Layer 2, consisting of three sub-layers that are the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the Medium Access Control (MAC) layer, and the Layer 1, also known as the Physical (PHY) layer.
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a carrier utilized in the LTE system. In the LTE system, the transmission from a UE to the network is achieved through a single uplink carrier and the transmission from the network to the UE is achieved through a single downlink carrier. As shown in FIG. 1, a carrier 11 has a control region 121, a data region 131, and a carrier indicator 111. The control region 121 carries one or multiple control signals, e.g. the control signal 101. The data region carries system data, user data, and/or other information. The carrier indicator 111 indicates that the carrier 11 is the carrier on which the data region 131 is controlled by control signals, e.g. the control signal 101, in the control region 121.
In the LTE system, for example, since there is no any other carrier except the carrier 11 for a transmission between the UE and the network, the control signals, e.g. the control signal 101, in the control region 121, are undoubtedly designated to the carrier 11 and therefore the carrier indicator 111 is not necessarily required.
Recently, the 3GPP is involved in the further advancements for E-UTRA and proposes an LTE-Advanced system as an enhancement of the LTE system. The LTE-Advanced system introduces the concept of Carrier Aggregation (CA), where two or more carriers are aggregated, in order to support wider transmission bandwidths, e.g. up to 100 MHz and for spectrum aggregation. A UE of the LTE-Advanced system can simultaneously receive and/or transmit on multiple carriers. However, in the LTE-Advanced system, the relations between the carrier indicators, multiple carriers, the control regions, and the data regions, are not specified.